Optical apparatus

ABSTRACT

A first surface of an optical component has a lens function of converging the transmission light from a light source. A second surface reflects the transmission light, converged by the lens function of the first surface, towards an end face of an optical transmission medium as the destination of transmission. The light reflected by the second surface is radaited from a coupling surface. Since the light beam from the light source is directed towards the optical transmission medium by exploiting the total reflection of light, a high-reflection multi-layer film or a polarization beam splitter film, required in a conventional apparatus employing a polarization beam splitter, is unneeded, with the result that the film forming cost or the cost in bonding two prisms used for fabricating the polarization beam splitter may be dispensed with. In this manner, the production cost or size of the apparatus can be reduced without lowering the transmission/reception performance.

TECHNICAL FIELD

[0001] This invention relates to an optical apparatus suitable fortransmission/reception of e.g., signal light for optical communication.

BACKGROUND ART

[0002] In these years, in keeping up with information diversification,thus is with the tendency towards multi-media, development of asmall-sized, high-performance low-cost communication apparatus hasbecome a desideratum. The optical communication by a two-core opticalfiber, having a glass optical fiber for transmission and a glass opticalfiber for reception, has already been put to practical use because itpermits high transmission rate and long-distance transmission and alsobecause it is strong against electromagnetic noise. However, in theoptical communication employing the two-core optical fiber, the opticalfiber and the communication apparatus are both expensive, such that itis not used extensively in households and finding only limited practicalapplication. Thus, the recent tendency is towards communicationemploying a sole inexpensive plastic optical fiber, such thatpreparations are being made for a communication environment by auni-core optical fiber.

[0003]FIGS. 37 and 38 mainly show the schematic structure of opticalcomponents of a conventional optical communication apparatus employing auni-core optical fiber. FIGS. 37 and 38 show an optical path L11 of thetransmitting light along with the schematic structure of an opticalsystem of the optical communication apparatus and an optical path L12 ofthe transmitting light along with the schematic structure of the opticalsystem of the optical communication apparatus.

[0004] As shown in these figures, the optical system of thecommunication apparatus includes a light source 101 constructed by e.g.,a semiconductor laser for radiating a transmitting laser light beam, anda collimator lens 102 for converting the light from the light source 101into collimated light and for radiating a collimated light beam. Theoptical system also includes a polarization beam splitter 103 forreflecting the S-polarized component of the incident light substantiallyby total reflection and transmitting a P-polarized component of theincident light substantially by total transmission. The optical systemalso includes a coupling lens 104 for converging the transmitting lightradiated from the polarization beam splitter 103 on an end face 105 a ofa uni-core optical fiber 105 and for radiating the received lightradiated from the end face 105 a of the optical fiber 105 as acollimated light beam. The optical system also includes a converginglens 106 for converging the collimated light beam radiated from thecoupling lens 104, and a photodetector 107 for detecting the receivedlight converged by the converging lens 106. The polarization beamsplitter 103 includes an inclined surface 103 a on the surface of whicha dielectric multilayer film is formed for imparting a polarization beamsplitter function, that is for reflecting an S-polarized light componentof the incident light substantially by total reflection and fortransmitting a P-polarized light component thereof substantially bytotal transmission. In the transmitting/reception device, the lightsource 101 and the polarization beam splitter 103 are arranged so thatthe plane of polarization of light radiated from the light source 101 tofall on the inclined surface 103 a will the S-polarization plane. Thus,the light from the light source 101 (S-polarized light) undergoessubstantially total reflection on the inclined surface 103 a.

[0005] In the above-described circuit apparatus, employing thepolarization beam splitter 103, bidirectional optical communication,that is transmission and reception employing the laser light, becomespossible with the use of a sole device.

[0006] The optical communication in the transmission apparatus capableof bidirectional optical communication occurs as follows:

[0007] Referring first to FIG. 37, when light is transmitted from thecircuit apparatus, the transmitting light is radiated from a lightsource 101 and collimated by the collimator lens 102 to fall on thepolarization beam splitter 103. Since the light source 101 and thepolarization beam splitter 103 are arranged relative to each other sothat the plane of polarization of the light radiated from the lightsource 101 to fall on the inclined surface 103 a will be the P-polarizedlight, the light radiated from the light source 101 is reflectedsubstantially by total reflection by the inclined surface 103 a. Thelight beam reflected by total reflection by the inclined surface 103 afalls on the end face 105 a of the optical fiber 105 via the couplinglens 104. The light incident on the optical fiber 105 is transmittedthrough the optical fiber 105 to the destination of communication as thesignal light for communication.

[0008] Referring to FIG. 38, the signal light transmitted through theoptical fiber 105 at the time of light reception by the communicationapparatus is radiated from the end face 105 a of the optical fiber 105.The light beam of the signal light radiated from the end face 105 a iscollimated by the coupling lens 104 of the communication apparatus so asto fall on the polarization beam splitter 103. The light beam incidenton the polarization beam splitter 103 has a random plane of polarization(light of random polarization). Of the light beam incident on thepolarization beam splitter 103, the S-polarized light component isreflected substantially by total reflection by the inclined surface 103a so as to be radiated towards the light source 101 as the so-calledfeedback light. On the other hand, of the light beam incident on thepolarization beam splitter 103, the P-polarized light is transmittedthrough the inclined surface 103 a substantially by total transmissionto exit the polarization beam splitter 103. The light radiated from thepolarization beam splitter 103 is converged by the converging lens 106on the photodetector 107, which then detects the light converged by theconverging lens 106 on photoelectric conversion as a reception signal.

[0009] Thus, with the communication apparatus shown in FIGS. 37 and 38,employing the polarization beam splitter 103, bidirectional opticalcommunication employing the laser light becomes possible even though noother device is used.

[0010] The polarization beam splitting function of the above-describedpolarization beam splitter is realized by forming a film structuredescribed below on an optical component.

[0011] As the technique of adding an optical function, such as theabove-mentioned polarization beam splitter unction, to an opticalelement, the operation of optical interference, as occurs when settingthe film thickness of a transparent thin film to a value of the numberof orders of light wavelength, is frequently used.

[0012] It is noted that the condition of interference when the lightfalls on the sole layer film in a perpendicular direction is shown bythe following equation:

n×d=m(¼)×λ

[0013] where λ is the light wavelength, n the refractive index of amonolayer film, m an number of orders of interference and d is aphysical film thickness. In general, in the above equation, n×d istermed the optical film thickness, while the number of orders ofinterference m is termed the phase thickness of a quarter wave opticalthickness (QWOT). For example, in the case of a thin film in which thewavelength λ of the light used is 550 nm, the refractive index of themonolayer of 2.3 and the physical film thickness d of 59.78 nm, theoptical film thickness (n×d) is 137.5 nm, with the optical filmthickness, that is the number of orders of interference m, being 1.

[0014] Meanwhile, if a single coating or a monolayer is formed on asubstrate as an optical element, there are two boundary surfaces havingdifferent refractive indexes between the air and the film, that is aboundary surface between the air and the film (first boundary surface),and a boundary surface between the film and a substrate of the opticalelement (secondary surface). If, in such case, the phase thickness, thatis the number of orders of interference m, is an odd number, phasedeviation π occurs, so that, as may be seen from the above equation, thereflected waves from the first boundary surface (boundary surfacebetween air and the film) and the reflected waves from the secondboundary surface (the boundary surface between the film and thesubstrate) interfere with each other to give the operation of thereflected waves cancelling each other to a maximum extent. On the otherhand, if the phase thickness, that is the value of the number of ordersof interference m, is an even number, the phase matching occurs, sothat, as may be seen from the above equation, the reflected waves fromthe first boundary surface (boundary surface between the air and thefilm) and those from the second boundary surface (boundary surfacebetween the film and the substrate) reinforce each other. Meanwhile, ifthe value of the phase thickness, that is the number of orders ofinterference m, is not an integer, there is produced an action lyingintermediate between the case where the number of orders of interferenceis an odd number and that where the number of orders of interference isan even number. Thus, it may be seen that the action of lightinterference can be controlled by changing the value of the refractiveindex of the film and the value of the physical film thickness d.

[0015] In the above-described polarization beam splitter 103, there isused a thin film structure by multiple layers obtained on alternatelylayering a thin film of high refractive index and a thin film of lowrefractive index. The interference operation in the case of themulti-layer film is hereinafter explained.

[0016] The optical properties by the action of light interference can becomputed by a matrix method employing the optical impedance. Forexample, if the film refractive index is n, film thickness is d and anangle of incidence of light to the film is θ, the characteristic matrixof a transparent monolayer film can be expressed by the followingtwo-row two-column four-terminal matrix: $M = \begin{bmatrix}{m11} & {m12} \\{m21} & {m22}\end{bmatrix}$

[0017] where m11, m22 are represented by cos g (m11=m22=cos g), m12 isrepresented by i·sin g/u (m12=i·u·sin g) and m21 is represented byi·u·sin g (m21=i·u·sin g). On the other hand, g is represented by2·π(n·d·cos θ)/λ (g=2·π(n·d·cos θ)/λ). For S-polarized light and forP-polarized light, u=n·cos θ and u=n·secθ, respectively.

[0018] The characteristic matrix M of a multi-layer film is representedby the product of characteristic matrices M1, M2, . . . , Mi, where i isan integer not less than 1, as indicated by the following equation:

M=(M 1)×(M 2)×. . . ×(Mi).

[0019] At this time, the reflectance R of the multi-layer film may becalculated, from the respective elements of the above-mentioned productof the characteristic matrices, the refractive index n0 of an incidentmedium and a refractive index ns of the substrate, by the followingequation:$R = {\frac{{\left( {{m11} + {i \cdot {m12} \cdot {us}}} \right) \cdot {u0}} - \left( {{i \cdot {m21}} + {{m22} \cdot {us}}} \right)}{{\left( {{m11} + {i \cdot {m12} \cdot {us}}} \right) \cdot {u0}} + \left( {{i \cdot {m21}} + {{m22} \cdot {us}}} \right)}}^{2}$

[0020] where u0=n0·cos θ0, us=ns·cos θs for the S-polarized lightcomponent and u0=n0·secθ0, us=ns·secθs for the S-polarized lightcomponent.

[0021] The above-described polarization beam splitter 103 may berealized by an alternate layering structure of two sorts of thin-filmmaterials having refractive indices satisfying the so-called Brewstercondition.

[0022] A more specified illustrative designing of a polarization beamsplitter is hereinafter explained.

[0023] It is assumed that a polarization beam splitter obtained onbonding two prisms having apex angles of 45° is to be designed as asubstrate of a polarization beam splitter. Also, in the presentembodiment, the desinging wavelength is 780 nm, and a vitreous materialfor a prism is SF11 (number of optical glass manufactured by SCHOTTINC.). A high refractive index thin film material used is TiO₂, with arefractive index of 2.30, whilst a low refractive index material used isSiO₂ with a refractive index of 1.46.

[0024] Since TiO₂ with the refractive index of 2.30 and SiO₂ with therefractive index of 1.46 are used as the high refractive index materialand the low refractive index material, respectively, as a filmcombination satisfying the Brewster condition, polarizationcharacteristics satisfying the functions of the polarization beamsplitter can be obtained by alternately layering TiO₂ and SiO₂ as shownbelow. It is noted that a multi-layer film composed of first tosixteenth layers is formed.

[0025] first layer TiO₂, d=93.9 nm, nd=216.0 nm

[0026] second layer SiO₂, d=147.9 nm, nd=215.9 nm

[0027] third layer TiO₂, d=93.9 nm, nd=216.0 nm

[0028] fourth layer SiO₂, d=147.9 nm, nd=215.9 nm

[0029] fifth layer TiO₂, d=93.9 nm, nd=216.0 nm

[0030] sixth layer SiO₂, d=147.9 nm, nd=215.9 nm

[0031] seventh layer TiO₂, d=93.9 nm, nd=216.0 nm

[0032] eighth layer SiO₂, d=147.9 nm, nd=215.9 nm

[0033] ninth layer TiO₂, d=93.9 nm, nd=216.0 nm

[0034] tenth layer SiO₂, d=147.9 nm, nd=215.9 nm

[0035] eleventh layer TiO₂, d=93.9 nm, nd=216.0 nm

[0036] twelfth layer SiO₂, d=147.9 nm, nd=215.9 nm

[0037] thirteenth layer TiO₂, d=93.9 nm, nd=216.0 nm

[0038] fourteenth layer SiO₂, d=147.9 nm, nd=215.9 nm

[0039] fifteenth layer TiO₂, d=93.9 nm, nd=216.0 nm

[0040] sixteenth layer SiO₂, d=147.9 nm, nd=215.9 nm

[0041] That is, of the first to sixteenth layers, odd-numbered layers,that is the first, third, fifth, seventh, ninth, eleventh, thirteenthand fifteenth layers, are of TiO₂, whilst even-numbered layers, that issecond, fourth, sixth, eighth, tenth, twelfth, fourteenth and sixteenthlayers are of SiO₂. Moreover, the physical thickness d of the TiO₂ layeras an odd-numbered layer is set to, for example, 93.9 nm, whilst thephysical thickness d of the SiO₂ layer as an even-numbered layer is setto, for example, 147.9 nm. In addition, an optical film thickness nd ofa TiO₂ layer as an odd-numbered layer is set to 216.0 nm, with opticalfilm thickness nd of a SiO₂ layer as an even-numbered layer is set to215.9 nm.

[0042] Meanwhile, the optical communication apparatus employing theabove-described polarization beam splitter suffers from the followingproblems:

[0043] First, the polarization beam splitter is in need of highoperational reliability, so that the multi-layered film needs to befabricated by an expensive electron beam evaporator, whilst there are alarge number of film layers and a prism needs to be bonded afterformation of the multi-layered film, thus increasing the manufacturingcost considerably.

[0044] On the other hand, the polarization beam splitter has suchoptical characteristics that it has high light incident angledependency, such that, in order to secure the signal to noise ratio ofthe communication light (communication signals), it is mandatory toprovide a collimator lens for collimating the light beam. Moreover, itis necessary to effect optical axis alignment.

[0045] In addition, the conventional optical communication apparatus hasa drawback that it has a large number of optical components to renderintegration difficult.

[0046] That is, the conventional optical communication apparatus has adrawback that its manufacturing cost is prohibitive and the apparatustends to be increased in size.

[0047] In view of the above-depicted problem of the prior art, it is anobject of the present invention to provide an optical apparatus whereby,if the apparatus is used as an optical communication apparatus, itreduces the cost and size of the apparatus without lowering thecommunication performance.

DISCLOSURE OF THE INVENTION

[0048] The present invention provides an optical apparatus including amain body unit of an optical apparatus, an optical transmission mediumconnector for connecting the optical transmission medium to the mainbody unit of the optical apparatus so that an end face of the opticaltransmission medium is at a pre-set angle with respect to the main bodyunit of the optical apparatus, a light emitting element fixed in themain body unit of the optical apparatus and adapted for radiating thelight, and a sole optical element having a second surface facing thefirst surface and a connecting surface interconnecting the first andsecond surfaces. The sole optical element is fixed to the main body unitof the optical apparatus. The first surface has the function ofconverging a light beam of light incident thereon from outside so thatthe light beam is focused at a position spaced a pre-set distance fromthe first surface. The light emitting element, optical component and theoptical transmission medium connector are secured in the main body unitof the optical apparatus in a relative position such that light radiatedfrom the light emitting element is incident on the optical component viathe first surface, the light incident on the first surface traverses theinside of the optical component, the light which has traversed theinside of the optical component is reflected on the second surface ofthe optical component towards the optical transmission medium connector,the light reflected on the second surface is radiated from the couplingsurface to outside the optical component, and the light outgoing fromthe coupling surface is focused on an end face of the opticaltransmission medium.

[0049] In the optical apparatus according to the present invention,there is also provided a light receiving element at a position lying onthe optical axis of the light radiated from the light transmissionmedium of the main body unit of the optical apparatus.

[0050] The optical component is arranged offset from the optical axis ofthe light radiated from the optical transmission medium.

[0051] The optical component is arranged on the optical axis of thelight radiated from the optical transmission medium. The light radiatedfrom the optical transmission medium falls on the coupling surface inthe optical component via the coupling surface to traverse the inside ofthe optical component to fall on the light receiving element.

[0052] The optical transmission medium connector connects the opticaltransmission medium at an angle with which the optical axis of the lightradiated from the optical transmission medium is inclined with respectto the optical axis direction of the light radiated from the lightemitting element to get to the second surface.

[0053] The optical transmission medium connector connects the opticaltransmission medium at an angle such that the optical axis of the lightradiated from the optical transmission medium is included in a planeperpendicular to the optical axis direction of light radiated from thelight emitting element to get to the second surface of the opticalcomponent.

[0054] The light receiving element is arranged on the opposite side ofthe light emitting element with respect to the second surface of theoptical component.

[0055] The light receiving element is arranged on the side of the lightemitting element with respect to the second surface and the lightradiated from the optical transmission medium falls on the opticalcomponent via the coupling surface to traverse the inside of the opticalcomponent to fall on the light receiving element.

[0056] The optical component has a diffractive pattern on the firstsurface.

[0057] The optical component further has a third surface which isprovided at an area between the second surface and the coupling surfacewhich is at least proximate to the optical transmission mediumconnector.

[0058] The first surface of the optical component is such that thecross-section obtained on slicing the optical component in a planepassing through a first optical axis of light radiated from the lightemitting element and getting to the second surface and through a secondoptical axis of light radiated from the optical transmission medium isconvexed towards the light emitting element.

[0059] The first surface of the optical component is such that thecross-section obtained on slicing the optical component in a first planeperpendicular to a second plane passing through a first optical axis oflight radiated from the light emitting element and getting to the secondsurface and through a second optical axis of light radiated from theoptical transmission medium is convexed towards the light emittingelement, with the first plane passing through the first optical axis.

[0060] The optical component has a substantially circularcross-sectional shape which is obtained on slicing the optical componentin a plane perpendicular to an optical axis of light radiated from thelight emitting element and getting to the second surface.

[0061] The second surface exhibits total reflection characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS

[0062]FIG. 1 shows schematics of an optical communication apparatusaccording to a first embodiment of the present invention.

[0063]FIG. 2 illustrates total reflection conditions of a reflectionsurface of an optical component in the optical communication apparatusshown in FIG. 1.

[0064]FIG. 3 illustrates a specified illustrative designing of anoptical component in the optical communication apparatus shown in FIG.1.

[0065]FIG. 4 is a perspective view of a casing of the opticalcommunication apparatus according to the present invention.

[0066]FIG. 5 is a cross-sectional view showing the optical communicationapparatus shown in FIG. 1, arranged in a casing.

[0067]FIG. 6 is a diagrammatic view showing schematics of an opticalcommunication apparatus according to a second embodiment of the presentinvention.

[0068]FIG. 7 is a cross-sectional view showing the optical communicationapparatus shown in FIG. 1, arranged in a casing.

[0069]FIG. 8 is a diagrammatic view showing schematics of an opticalcommunication apparatus according to a third embodiment of the presentinvention.

[0070]FIG. 9 is a cross-sectional view showing the optical communicationapparatus shown in FIG. 8, arranged in a casing.

[0071]FIG. 10 is a diagrammatic view showing schematics of an opticalcommunication apparatus according to a fourth embodiment of the presentinvention.

[0072]FIG. 11 is a cross-sectional view showing the opticalcommunication apparatus shown in FIG. 10, arranged in a casing.

[0073]FIG. 12 is a diagrammatic view showing schematics of an opticalcommunication apparatus according to a fifth embodiment of the presentinvention.

[0074]FIG. 13 is a cross-sectional view showing the opticalcommunication apparatus shown in FIG. 12, arranged in a casing.

[0075]FIG. 14 is a diagrammatic view showing schematics of an opticalcommunication apparatus according to a sixth embodiment of the presentinvention.

[0076]FIG. 15 is a cross-sectional view showing the opticalcommunication apparatus shown in FIG. 14, arranged in a casing, andlooking from the side of an arrow A in FIG. 15.

[0077]FIG. 16 is a cross-sectional view showing the opticalcommunication apparatus shown in FIG. 14, arranged in a casing, andlooking from the side of an arrow A in FIG. 15.

[0078]FIG. 17 is a diagrammatic view showing schematics of an opticalcommunication apparatus according to a seventh embodiment of the presentinvention.

[0079]FIG. 18 is a cross-sectional view showing the opticalcommunication apparatus shown in FIG. 17, arranged in a casing.

[0080]FIG. 19 is a diagrammatic view showing schematics of an opticalcommunication apparatus according to an eighth embodiment of the presentinvention.

[0081]FIG. 20 is a cross-sectional view showing the opticalcommunication apparatus shown in FIG. 19, arranged in a casing.

[0082]FIG. 21 is a diagrammatic view showing schematics of an opticalcommunication apparatus according to a ninth embodiment of the presentinvention.

[0083]FIG. 22 is a cross-sectional view showing the opticalcommunication apparatus shown in FIG. 21, arranged in a casing.

[0084]FIG. 23 is a diagrammatic view showing schematics of an opticalcommunication apparatus according to a tenth embodiment of the presentinvention.

[0085]FIG. 24 is a cross-sectional view showing the opticalcommunication apparatus shown in FIG. 23, arranged in a casing.

[0086]FIG. 25 is a perspective view showing a first specified embodimentof optical communication apparatus of the various embodiments of thepresent invention.

[0087]FIG. 26 is a perspective view showing an arrangement of respectiveconstituent elements of optical communication apparatus employing theoptical components of FIG. 25.

[0088]FIG. 27 is a see-through perspective view showing the state inwhich the optical communication apparatus employing the opticalcomponent of FIG. 25 is arranged in a casing.

[0089]FIG. 28 is a perspective view showing a second specifiedembodiment of optical communication apparatus of the various embodimentsof the present invention.

[0090]FIG. 29 is a perspective view showing an arrangement of respectiveconstituent elements of optical communication apparatus employing theoptical components of FIG. 28.

[0091]FIG. 30 is a see-through perspective view showing the state inwhich the optical communication apparatus employing the opticalcomponent of FIG. 25 is arranged in a casing.

[0092]FIG. 31 is a perspective view showing a third specified embodimentof optical communication apparatus of the various embodiments of thepresent invention.

[0093]FIG. 32 is a perspective view showing an arrangement of respectiveconstituent elements of optical communication apparatus employing theoptical components of FIG. 31.

[0094]FIG. 33 is a see-through perspective view showing the state inwhich the optical communication apparatus employing the opticalcomponent of FIG. 31 is arranged in a casing.

[0095]FIG. 34 is a perspective view showing a fourth specifiedembodiment of optical communication apparatus of the various embodimentsof the present invention.

[0096]FIG. 35 is a perspective view showing an arrangement of respectiveconstituent elements of optical communication apparatus employing theoptical components of FIG. 34.

[0097]FIG. 36 is a see-through perspective view showing the state inwhich the optical communication apparatus employing the opticalcomponent of FIG. 34 is arranged in a casing.

[0098]FIG. 37 is a diagrammatic view showing schematics of aconventional optical communication apparatus.

[0099]FIG. 38 is a diagrammatic view showing schematics of anotherconventional optical communication apparatus.

BEST MODE FOR CARRYING OUT THE INVENTION

[0100] Referring to the drawings, certain preferred embodiments of thepresent invention will be explained in detail.

[0101]FIG. 1 shows a schematic arrangement of an optical system, as amain portion of an optical communication apparatus 10 for opticalcommunication enabling transmission and reception of changes in lightintensity as an optical apparatus embodying the present invention. InFIG. 1, there are also shown an optical path L1 of the transmissionsystem and an optical path L2 of the reception system, along with thearrangement of the optical apparatus.

[0102] The optical communication apparatus 10 of the first embodimentincludes a light source 1, constituted by a seimconductor laser or alight emitting diodes to emit the transmission light for opticalcommunication, an optical component 2 for guiding the transmission lightfrom the light source 1 to an end face 4 a of an optical transmissionmedium 4 formed by, for example, a unit-core optical fiber, and aphotodetector 3 for detecting the receiving light emitted from the endface 4 a of the optical transmission medium 4 as reception signal.

[0103] In the present optical communication apparatus 10, shown in FIG.1, the light source 1, optical component 2 and the photodetector 3 arearranged in a congested configuration in different areas on a substrate11 of, for example, a semiconductor integrated circuit. The light source1 is arranged in a congested fashion on the substrate 11 via a supportbase 12. The photodetector 3 has its portion other than its detectionsurface buried in the bulk portion of the substrate 11 of, for example,a semiconductor integrated circuit, with a detection surface being on anoptical axis of the light radiated from the end face 4 a of the opticaltransmission medium 4 and being at a position facing the end face 4 a ofthe optical transmission medium 4.

[0104] Also, in the optical communication apparatus 10 of FIG. 1, thephotodetector 3 is arranged on an optical axis of the light radiatedfrom the end face 4 a of the optical transmission medium 4, whilst theoptical component 2 is arranged at a position offset from the opticalaxis of the reception light radiated from the end face 4 a of theoptical transmission medium 4. Stated differently, the respectiveconstituent elements of the optical communication apparatus 10 arearranged so that the reception light radiated from the end face 4 a ofthe optical transmission medium 4 is incident only on the photodetector3 without being incident on the optical component 2. Also, in theoptical communication apparatus 10 of the embodiment of FIG. 1, theoptical path L1 of the transmission system is arranged so as not to beoverlapped with the optical path L2 of the reception system.

[0105] The optical component 2 of the optical communication apparatus 10is formed of a sole transparent optical material and has a lens functionand a prism function. Meanwhile, the lens function in the opticalcomponent 2 means light beam converging, numerical aperture (NA)converting functions etc, and realizes the lens function of convergingthe light beam or converting the NA by the spherical surface,non-spherical surface or the shape of the diffraction lattice. Also, theprism function in the optical component 2 means the function of changingthe spatial direction of the light beam, such as reflection,transmission reflection or diffraction. Also, in the present embodiment,the reflection in the prism function of the optical component 2 meanstotal reflection of light occurring on the boundary surface between anoptically dense medium (medium of high refractive index) and anoptically sparse medium (medium of low refractive index) when the lightproceeding in the optically dense medium falls on the optically sparsemedium.

[0106] The optical component 2 includes a first surface S1 (lens surfaceS1) facing the light source 1 and adapted to converge the transmittedlight from the light source 1 at a position offset a pre-set distance,and a second surface S2 (reflecting surface S2) provided facing the lenssurface S1 and adapted to reflect the transmission light converged bythe lens function of the lens surface S1 towards the end face 4 a of theoptical transmission medium 4. The optical component 2 also includes abonding surface S3 to the substrate 11 and a surface S4 operating as aradiating surface for radiating the light reflected by the reflectingsurface S2. The surface S4 is referred to below as a coupling surface S4because it operates for coupling the first surface S1 to the secondsurface S2. Meanwhile, in the optical component 2, it is desirable forthe lens surface S1 and the coupling surface S4 to form ananti-reflective surface for reducing the stray light or optical loss.Also, the lens surface S1 and the coupling surface S4 may be subjectedin the optical component 2 to refractive index profile processing. Inparticular, the lens surface S1 is preferably provided with amulti-layer reflection preventative film to achieve anti-reflectioneffect over a wide angle of incidence.

[0107] Also, in the optical component 2, the lens surface S1 producingthe lens function has its focal length or the NA designed so that thelight beam emitted by the light source 1 will form a focal point on theend face 4 a of the optical transmission medium 4. In the opticalcomponent 2, the reflecting surface S2 is a surface responsible for theabove-mentioned prism function and is adapted for reflecting theincident light by the total reflection of light generated on theinterface between the optically dense medium and the optically sparsemedium. That is, this reflecting surface S2 is inclined at a pre-setangle with respect to the optical axis of the light radiated from thelight source 1 so as to produce total reflection of the incident light.

[0108] Referring to FIG. 2, the relation between the angle of incidenceto the reflective surface S2 of the optical component 2 and thecondition of total reflection of light by the reflecting surface S2.

[0109] For aiding in the understanding of the optical operation by theoptical component 2, it is assumed that the light beam of thetransmitted light from the light source 1 is the light beam only alongthe direction of the directive line, that is that the light beam of thetransmitted light is a collimated light beam. Meanwhile, the directionof the directive line means the center vector direction of the lightbeam from the light source 1.

[0110] The angle of incidence θi of the transmitted light on thereflecting surface S2 is expressed by the equation (A):

θi=θ ₂₃−90°  (A)

[0111] where θ₂₃ is an angle between the reflecting surface S2 and thesurface S3. It is noted that the angle of incidence θi is an anglebetween a line of orientation P1 and a normal line P2 drawn to thereflecting surface S2. In FIGS. 1 and 2, the angle the reflectingsurface S2 makes with the surface of the substrate 11 is denoted with areference symbol θ₂₄.

[0112] On the other hand, critical angle θc of total reflection of lightis expressed by the following equation (B):

θc=sin ⁻¹(1/ng)  (B)

[0113] where ng is the refractive index of the optical component 2.

[0114] It is noted that, if the angle of incidence θi is larger than orequal to θc, that is if θi≧θc, total reflection occurs on the reflectingsurface S2. Therefore, the condition for the angle θ₂₃ is represented,from the equations A and B, by the following equation (C):

θ₂₃≧90°+sin⁻¹(1/ng)  (C).

[0115]FIG. 3 shows a computational example for angles θc and θ₂₃ in caseof applying a material routinely used as an optical material. In FIG. 3,there is shown a computational example for the angles θc and θ₂₃ in caseof application of a quartz glass and an optical glass BK7 and SF11,manufactured by SCHOTTS INC, as a material routinely used as an opticalmaterial. FIG. 3 shows computational examples for the angles θc and θ₂₃in case of applying the polymethyl methacrylate (PMMA) and polycarbonate(PC) as typical plastics materials for optical application. As may beseen from FIG. 3, it is sufficiently possible, in a majority of routineoptical materials, to realistically design the optical components 2 inwhich the reflecting surface S2 brings about total reflection. As mayalso be seen from FIG. 3, if a material of high refractive index is usedas the optical component 2, the critical angle θc is reduced to renderit possible to reduce the angle θ₂₃.

[0116] In the above explanation, the light beam incident on thereflecting surface S2 is assumed to be a collimated light beam. However,in actuality, the light beam incident on the reflecting surface S2 isthe light beam converged by the lens operation of the lens surface S1,so that the angle of incidence on the reflecting surface S2 has anangular extent determined by the angle of convergence of the light beamand hence there is a risk that a light beam be produced which is not inmeeting with the condition for total reflection. If, on the other hand,the laser light is used as the transmitting light, the intensity of thelaser light exhibits the Gaussian distribution, such that the centerintensity is high whilst the intensity on the skirts is extremely low.Therefore, if in actuality the angle θ₂₃ is increased with theconverging angle Δθ (half angle) as an offset, ideal total reflection isachieved even with the converging light beam. If, on the other hand, thedevice size is to be decreased at the cost of the S/N ratio of thedevice to a slight extent, the angle θi (=θ₂₃−90°) may be equal to thecritical angle θc of total reflection without taking the angle ofconvergence into account. The light of an angular range for which theincidence angle of the light beam to the reflecting surface S2 is notlarger than the critical angle θc is in the skirt range of the laserlight exhibiting the Gaussian distribution, that is the range where thelight intensity is extremely low, so that a sufficiently usable S/Nratio can be obtained.

[0117] In the optical transmission apparatus, constructed as shown inFIG. 1, the light transmitting and receiving operation is the following:

[0118] First, or light transmission from the optical transmissionapparatus, the transmitting light is radiated from the light source 1.The light beam of the transmitted light, radiated by the light source 1,is converged by the lens surface S1 of the optical component 2, arrangedfacing the light source 1, and proceeds through the interior of theoptical component 2. The light beam incident from the lens surface S1 istotally reflected by the reflecting surface S2 and radiated via couplingsurface S4 towards an end face 4 a of the optical transmission medium 4.The light beam radiated from the optical component 2 forms an image onthe end face 4 a of the optical transmission medium 4 by the lensoperation of the lens surface S1. The light beam incident on the endface 4 a proceeds as transmission signal through the opticaltransmission medium 4 and gets to an optical transmission apparatus ofthe destination of transmission.

[0119] For light reception in the present optical transmissionapparatus, the signal light transmitted through the optical transmissionmedium 4 is radiated from the end face 4 a of the optical transmissionmedium 4. The signal light radiated from the end face 4 a is radiated onthe photodetector 3. This photodetector 3 photo-electrically convertingthe incident light, while detecting changes in the intensity of theincident light. The signal light incident on the end face 4 a of theoptical transmission medium 4 and transmitted through the opticaltransmission medium 4 is detected as a received signal. Preferably, ananti-reflection film or a filter film transmitting only the signal light(received light) is provided on the surface of the photodetector 3 totransmit only the wavelength of the received light to reduce the opticalloss to remove stray light. By providing the filter film or the like, itis possible for the photodetector 3 to detect substantially the totalityof the received light to improve the S/N ratio of the apparatus at thetime of reception.

[0120] The above-described optical communication apparatus, embodyingthe present invention, is arranged in a casing 20 shown for example inFIG. 4. To the casing 20 can be connected the optical transmissionmedium 4 as an optical fiber vis a connector 21.

[0121]FIG. 5 shows a cross-sectional view of the components parts ofFIG. 1 arranged in the casing 20 of FIG. 4. In FIG. 5, a substrate 11,on which are assembled the support base 12, optical component 2 and thephotodetector 3, is secured to the inner bottom surface of the casing20. On the connector 21 is mounted an optical fiber as the opticaltransmission medium 4. The relation between the fixed position of thesubstrate 11 and the arranging position of the connector 21 on thecasing is such that the photodetector 3 on the substrate 11 is on theoptical axis of the light radiated from the end face 4 a of the opticaltransmission medium 4 mounted on the connector 21.

[0122] In the optical communication apparatus 10 of the firstembodiment, described above, in which the respective optical elementsare arranged so that the optical path L1 of the transmission system willnot be overlapped with the optical path R2 of the receiving system, thepolarization beam splitter for separating the transmitting light fromthe receiving light, so far used in the conventional opticalcommunication apparatus, becomes unnecessary. Also, in the opticalcommunication apparatus 10 of the first embodiment, since the light beamfrom the light source 1 is guided towards the optical transmissionmedium 4 by exploiting the phenomenon of total reflection of lightgenerated on the boundary surface (reflecting surface S2) on lightincidence from an optically dense transparent medium to a roughtransparent optical medium, it is unnecessary to form a high reflectionmulti-layered film or a polarization beam splitter film, incontradistinction from the conventional apparatus employing thepolarization beam splitter, thus enabling reduction in costs, such asthe cost in forming films or in bonding two prisms used formanufacturing polarization beam splitters.

[0123] Also, in the present first embodiment, in which the action oftotal reflection of light on the reflecting surface S2 of the opticalcomponent 2 is exploited, the light is reflected on the reflectingsurface S2 at 100% reflectance, without regard to the angle of lightincidence, insofar as the condition for total light reflection is met.The reflection on the reflecting surface S2 exhibits extremely smallincident angle dependency, so that, if substantially the totality of theconverged light from the lens surface S1 is reflected by the reflectingsurface S2, the transmitted light suffers from only small loss, as aresult of which the deterioration of the S/N ratio is evaded. Thus, inthe present first embodiment, the collimator lens for maintaining theS/N ratio as required in the conventional device is not needed to renderit possible to diminish the number of components. Moreover, since theoptical communication apparatus of the present first embodiment uses theoptical component 2 having both the lens and prism functions and whichintegrates the functions of plural optical components, the number of theoptical components can be diminished, at the same time as integrationwith semiconductor components such as the light source 1 or thephotodetector 3 of the semiconductor laser is facilitated to render itpossible to reduce the size of the apparatus and the assembling cost.Also, since the optical component 2, as a sole component, has thefunction as a lens and that as a prism, in combination, it isunnecessary to have plural components, such as polarization beamsplitter, as in the conventional device, so that the optical component 2can be manufactured by a method having high mass-producibility, such asglass pressing or injection molding of plastics, thus enabling costreduction.

[0124] In addition, in the present embodiment of the opticalcommunication apparatus, since the optical path L1 of the transmittingsystem is not overlapped with the optical path Reflecting surface S2 ofthe reception system, and hence there is no return light of the receivedlight to the light source 1, no laser noise is produced. Moreover, theconventional apparatus employing the polarization beam splitter discardsthe S-polarized component of the received light, thus deteriorating theS/N ratio at the time of reception. Conversely, the present embodimentof the optical communication apparatus, employing an optical systemexhibiting no polarization dependency of light, has a superior S/N ratioat the time of reception.

[0125] Thus, in the present embodiment, the apparatus can be reduced insize and cost without lowering the transmission and receptionperformance.

[0126] Referring to FIGS. 6 and 7, a second embodiment of the presentinvention is explained. In the following description, parts orcomponents which are the same as those of the first embodiment aredepicted by the same reference symbols and are not explainedspecifically.

[0127]FIG. 6 shows schematics of an optical communication apparatus 10Aaccording to a second embodiment of the present invention. In theabove-described first embodiment, the optical component 2 and thephotodetector 3 are arranged on respective different areas in thesubstrate 11. In the present second embodiment of the opticalcommunication apparatus 10A, the optical component 2 is arranged on thesame area on the substrate 11 as that in which the photodetector 3 isburied in the substrate 11. Stated differently, the optical component 2is arranged on the optical axis of the received light, radiated from theend face 4 a of the optical transmission medium 4 is incident via thecoupling surface S4 of the optical transmission medium 4 to traverse theinterior of the optical component 2 to fall on the photodetector 3.Also, in the present second embodiment, the optical component 2 and thephotodetector 3 are arranged so that the optical component 2 has itssurface S3 bonded to a detection surface of the photodetector 3.

[0128] Thus, in the present second embodiment, the signal light,transmitted by the optical transmission medium 4, is radiated from theend face 4 a of the optical transmission medium 4 to fall on the opticalcomponent 2 via the coupling surface S4. The light incident from thecoupling surface S4 on the optical component 2 is radiated from thesurface S3 to reach the photodetector 3 so as to be detected as areception signal.

[0129] In the present embodiment, the device can be smaller in size thanthe device of the first embodiment by arranging the optical component 2and the photodetector 3 in the same region of the substrate 11.

[0130] Meanwhile, in the present second embodiment, the opticalcomponent 2 is secured to the photodetector 3. As an adhesive, atransparent adhesive is used to prevent the detection performance of thephotodetector 3 from being lowered. Also, in the present embodiment,since the received light falls on the coupling surface S4 of the opticalcomponent 2 to get to the photodetector 3 via the surface S3, the latteris preferably processed for preventing light reflection. If the surfaceS3 is to be processed for reflection prevention, it is preferred toperform reflection prevention processing taking into account therefractive index and the thickness of the transparent adhesive.

[0131] Also, in the present second embodiment, it is preferred to use amaterial of a refractive index higher than that of the material used inthe first embodiment. If the material of a higher refractive index isused, the critical angle θc of total reflection on the reflectivesurface S2 is decreased such that the condition for total reflection onthe reflecting surface S2 of the totality of the light beams incident onthe reflecting surface S2 is more liable to be met. Also, in the case ofthe optical component 2, formed of a high refractive index material, therefractive power on the lens surface S1 can be increased, as thecondition for total reflection on the lens surface S1 is met, so that itis possible to reduce the focal length from the lens surface S1 to theend face 4 a of the optical transmission medium 4 and hence to reducethe size of the apparatus.

[0132] Referring to FIG. 7, the optical communication apparatus 10A ofthe above-described second embodiment is arranged in the casing 20Asimilar to that shown in FIG. 4. Meanwhile, FIG. 7 shows a cross-sectionof the components of FIG. 6 arranged in the casing 20A. In the followingdescription, parts or components which are the same as those of thefirst embodiment are depicted by the same reference symbols and are notexplained specifically.

[0133] In the second embodiment, the relative position between themounting position of the substrate 11 and a connector 21A is such thatthe optical component 2 and the photodetector 3 on the substrate 11 willbe arranged on the optical axis of the light radiated from the end face4 a of the optical transmission medium 4 mounted on the connector 21A.

[0134] In the above-described second embodiment of the opticalcommunication apparatus 10A, in which the optical component 2 and thephotodetector 3 are arranged on the same area of the substrate 11, theapparatus can be furtherreduced in size.

[0135] Also, with the present second embodiment of the opticalcommunication apparatus 10A, as in the first embodiment, thepolarization beam splitter, so far used for separating the transmissionlight and the reception light from each other, becomes unnecessary, sothat it becomes unnecessary to form a high reflection multi-layered filmor a polarization beam splitter film, thus allowing to reduce the costsincurred in film deposition or bonding two prisms used for manufacturingthe polarization beam splitter. Moreover, in the present secondembodiment, as in the first embodiment, the transmission light can bereflected substantially in its entirety on the reflecting surface S2, sothat loss in the transmission light is reduced, while a collimator lensfor assuring the S/N ratio performance as required in the conventionalapparatus is redundant to render it possible to reduce the number ofcomponents. Also, in the optical communication apparatus 10A of thesecond embodiment, as in the first embodiment, the optical component 2,which has integrated plural optical components, is used, thus allowingto reduce the number of optical components, the size of the apparatusand the assembling costs and to facilitate integration of respectivecomponents. Moreover, the optical component 2 can be produced by amanufacturing method of high mass-producibility to allow for costreduction. Also, in the optical communication apparatus 10A of thesecond embodiment, similarly to the first embodiment, there is no returnlight of the reception light to the light source 1, no laser noise etcis produced. Moreover, the S/N ratio on reception is excellent becausethe optical system having no light polarization dependency is used.

[0136] Referring to FIGS. 8 and 9, a third embodiment of the presentinvention is explained. In the following description, parts orcomponents which are the same as those of the first embodiment aredepicted by the same reference symbols and are not explainedspecifically.

[0137]FIG. 8 shows schematics of the optical communication apparatus 10Baccording to an embodiment of the present invention. In the opticalcommunication apparatus 10B of the present third embodiment, thephotodetector 3 is arranged on the optical axis of the reception lightradiated from the end face 4 a of the optical transmission medium 4,whilst the optical component 2 is arranged at a position offset from theoptical axis of the reception light radiated from the end face 4 a ofthe optical transmission medium 4.

[0138] Also, in the present third embodiment, an angle θ₂₃, which thereflecting surface S2 of the optical component 2 makes with the surfaceS3 is set to 135°, that is the angle the reflecting surface S2 makeswith the surface of the substrate 11 is set to 45°. At this time, thematerial of the optical component 2 needs to be such a material assatisfies the conditions for total reflection even with the angle θ₂₃ of135°. Meanwhile, the optical materials shown in FIG. 3 all satisfy theconditions for total reflection even if the angle θ₂₃ is set to 135°. Itis noted that the ant-reflection processing needs to be performed on thelens surface S1 and the coupling surface S4.

[0139] Since the angle θ₂₃ is set in the present third embodiment to135°, the light converging position of the transmission light issubstantially directly above the reflecting surface S2. Therefore, theend face 4 a of the optical transmission medium 4 is arrangedsubstantially directly above the reflecting surface S2. However, theoptical transmission medium 4 is tilted so that the optical axis of thereception light radiated from the optical transmission medium 4 will beoutside the optical component 2 with respect to the light source 1.Since the optical transmission medium 4 has its end tilted, in thepresent third embodiment, the signal light transmitted by the opticaltransmission medium 4 is radiated from the end face 4 a of the opticaltransmission medium 4 so as to be radiated on the photodetector 3without falling on the optical component 2.

[0140] The optical communication apparatus 10B of the above-describedthird embodiment is arranged in the casing 20B, as shown in FIG. 9. FIG.9 shows a cross-section of the respective components of FIG. 8 enclosedin the casing 20B.

[0141] In the present third embodiment, the connector 21B connects theoptical transmission medium 4 at an angle such that the optical axis ofthe radiated light from the end face 4 a of the optical transmissionmedium 4 is inclined with respect to the plane perpendicular to thedirection of the optical axis of the transmission light radiated fromthe light source 1 to get to the reflecting surface S2 of the opticalcomponent 2. That is, in the present third embodiment, the connector 21Bis arranged so that the optical transmission medium 4 will be arrangedobliquely relative to the casing 20B. Also, the connector 21B isarranged with a tilt relative to the optical component 2 and thephotodetector 3 so that the endface 4 a of the optical transmissionmedium 4 mounted on the connector 21B faces the reflecting surface S2 ofthe optical component 2, the optical axis of the reception lightradiated from the optical transmission medium 4 is outside the opticalcomponent 2 with respect to the light source 1, and so that the radiatedlight from the optical transmission medium 4 will fall only on thephotodetector 3 without falling on the optical component 2.

[0142] With the above-described third embodiment of the opticalcommunication apparatus 10B, in which the angle θ₂₃ in the reflectingsurface S2 of the optical component 2 is set to 135°, the opticalcomponent 2 can be manufactured easily at a low cost.

[0143] Referring to FIGS. 10 and 11, a fourth embodiment of the presentinvention is explained. In the following description, parts orcomponents which are the same as those of the first embodiment aredepicted by the same reference symbols and are not explainedspecifically.

[0144]FIG. 10 is a diagrammatic view showing the schematics of anoptical communication apparatus 10C according to the fourth embodimentof the present invention. The optical communication apparatus 10C of thethird embodiment has both the feature of the above-described second andthirds embodiments. That is, in the present fourth embodiment of theoptical communication apparatus 10C, the optical component 2 is arrangedon the optical axis of the reception light radiated from the end face 4a of the optical transmission medium 4, the reception light radiatedfrom the end face 4 a of the optical transmission medium 4 will beincident on the coupling surface S4 of the optical component 2 to fallon the photodetector 3 via the interior of the optical component 2 andthe angle θ₂₃ on the reflecting surface S2 of the optical component 2 isset to 135° C.

[0145] In the present fourth embodiment, the optical transmission medium4 is arranged so as to directly overlie the reflecting surface S2 of theoptical component 2, while being tilted at a distal end thereof so thatthe light beam of the reception light radiated from the end face 4 awill be incident from the coupling surface S4 to get to thephotodetector 3 via the surface S3 without falling on the reflectivesurface S2. Meanwhile, in the present fourth embodiment, the directionof tilt of the optical transmission medium 4 is opposite to that in thethird embodiment.

[0146] In the present fourth embodiment, the signal light transmitted bythe optical transmission medium 4 tilted in the opposite direction tothat in the third embodiment is radiated from the end face 4 a of theoptical transmission medium 4 to fall on the optical component 2 via thecoupling surface S4. The light incident on the optical component 2reaches the photodetector 3 via the surface S3 so as to be detected bythis photodetector 3 as a reception signal.

[0147] The optical communication apparatus 10C of the above-describedfourth embodiment is arranged in the casing 20C, as shown in FIG. 11.FIG. 11 shows a cross-section of the respective component parts of FIG.10 arranged in the casing 20C.

[0148] In the present fourth embodiment, the connector 21C connects theoptical transmission medium 4 at an angle with which the optical axis ofthe light radiated at the end face 4 a of the optical transmissionmedium 4 is inclined relative to the casing 20C. That is, in the presentfourth embodiment, the connector 21C is provided so that the opticaltransmission medium 4 will be inclined obliquely relative to the casing20C. The connector 21C is located relative to the optical component 2and the photodetector 3 so that the end face 4 a of the opticaltransmission medium 4 mounted on the connector 21C is inclined in anopposite direction to that in the embodiment of FIG. 9 and so that theoptical component 2 and the photodetector 3 will be arranged on theoptical axis of the light radiated from the end face 4 a of the opticaltransmission medium 4 mounted on the connector 21C.

[0149] With the above-described fourth embodiment of the opticalcommunication apparatus 10C, since the optical component 2 and thephotodetector 3 are arranged on the same area of the substrate 11, andthe angle θ₂₃ on the reflecting surface S2 of the optical component 2 isset to 135°, it is possible to reduce the size and the cost of theapparatus further.

[0150] Also, with the above-described fourth embodiment of the opticalcommunication apparatus 10C, as in the first to third embodiments, it ispossible to reduce the size and the production cost of the apparatus,while it is possible to reduce the deterioration in the signal S/Nratio.

[0151] Referring to FIGS. 12 and 13, a fifth embodiment of the presentinvention is explained. In the following description, parts orcomponents which are the same as those of the first embodiment aredepicted by the same reference symbols and are not explainedspecifically.

[0152]FIG. 12 is a diagrammatic view showing the schematics of anoptical communication apparatus 10F according to the fifth embodiment ofthe present invention. In the present fifth embodiment, thephotodetector 3 is arranged between the light source 1 and the opticalcomponent 2. In the present fifth embodiment, the optical transmissionmedium 4 is arranged at a pre-set tilt so that the reception lightradiated from the end face 4 a will be illuminated on the photodetector3. Specifically, with the present fifth embodiment, the photodetector 3is arranged on the optical axis of the reception light radiated from theend face 4 a of the optical transmission medium 4, whilst the opticalcomponent 2 is arranged at a position offset from the optical axis ofthe reception light radiated from the end face 4 a of the opticaltransmission medium 4.

[0153] The arrangement of the present fifth embodiment is suitably usedif, due to the constraint form apparatus designing, the photodetector 3cannot be arranged opposite side of the reflecting surface S2 of theoptical component 2 looking from the light source 1 as in theabove-described first and third embodiments, or if it is desired toprevent the lowering of the light volume of the reception light causedby providing the photodetector 3 below the optical component 2.

[0154] The optical communication apparatus 10F is arranged within thecasing 20F, as shown in FIG. 13, showing the respective component partsof FIG. 12 arranged in the casing 20F in a cross-sectional view.

[0155] In the present fifth embodiment, the connector 21F connects theoptical transmission medium 4 at an angle with which the optical axis ofthe light radiated from the end face 4 a of the optical transmissionmedium 4 is inclined relative to the plane perpendicular to thedirection of the optical axis of the transmission light radiated fromthe light source 1 to get to the reflecting surface S2 of the opticalcomponent 2. That is, in the present fifth embodiment, a connector 21Fis provided for connecting the optical transmission medium 4 obliquelyrelative to the casing 20F. Also, the connector 21F is arranged so thatthe optical axis of the light radiated from the end face 4 a of theoptical transmission medium 4 mounted on the connector 21F is on thephotodetector 3 arranged between the light source 1 and the opticalcomponent 2.

[0156] In the fifth embodiment of optical communication apparatus 10F,in which the photodetector 3 can be arranged between the photodetector 3and the optical component 2, it is possible to raise the degree offreedom in apparatus designing to prevent the lowering of the lightvolume of the reception light.

[0157] With the fifth embodiment of the optical communication apparatus10F, as with the first to fourth embodiment, it is possible to reducethe size and the production cost of the apparatus, while it is possibleto prevent the signal S/N ratio from being lowered.

[0158] Referring to FIGS. 14 to 16, a sixth embodiment of the presentinvention is explained. In the following description, parts orcomponents which are the same as those of the first embodiment aredepicted by the same reference symbols and are not explainedspecifically.

[0159]FIG. 14 is a diagrammatic view showing the schematics of anoptical communication apparatus 10G according to the sixth embodiment ofthe present invention. In the present sixth embodiment, thephotodetector 3 is arranged on the optical axis of the reception lightradiated from the end face 4 a of the optical transmission medium 4,whilst the optical component 2 is arranged at a position offset from theoptical axis of the reception light radiated from the end face 4 a ofthe optical transmission medium 4. In addition, the arranging angle ofthe optical transmission medium 4 is tilted so that the optical axis ofthe reception light radiated from the optical transmission medium 4 willbe inclined relative to the plane which contains the optical axisradiated from the light source 1 to get to the reflecting surface S2 andwhich is perpendicular to the substrate 1. Meanwhile, the reflectingsurface S2 of the optical component 2 is inclined so that the anglebetween it and the substrate 11 will be equal to the aforementionedangle θ₂₃.

[0160] The optical communication apparatus 10G of the above-describedfourth embodiment is arranged in a casing 20G, as shown in FIG. 15,showing a cross-section of the respective component parts of FIG. 14arranged in the casing 20G. Meanwhile, FIG. 16 shows a cross-sectionshowing the state in which the optical communication apparatus 10G ofthe sixth embodiment is arranged in the casing 20G, with the opticalcommunication apparatus 10G being viewed from the direction of an arrowA in FIG. 15.

[0161] That is, in the present sixth embodiment, the connector 21G isarranged on the casing 20, so that the optical axis of the receptionlight radiated from the end face 4 a of the optical transmission medium4 will be inclined relative to the plane containing the optical axis ofthe light radiated from the light source 1 to get the reflecting surfaceS2 and which is perpendicular to the substrate 11, as shown in FIGS. 15and 16.

[0162] The optical communication apparatus 10G of the present sixthembodiment is suitably employed if, due to constraint in apparatusdesigning, the connector 21G cannot be arranged at right angles to thecasing surface, as when the optical transmission medium 4 cannot bearranged at right angles to the casing surface, or if the photodetector3 cannot be arranged on a plane containing the optical axis of the lightradiated from the light source 1 to get to the reflecting surface S2 andwhich is normal to the substrate 1.

[0163] With the present sixth embodiment, the configuration of theabove-described third to fifth embodiments can be used in combination.That is, in the above-described third to fifth embodiments, as in thesixth embodiment, the arranging angle of the optical transmission medium4 can be tilted so that the optical axis of the reception light radiatedfrom the optical transmission medium 4 will be inclined with respect tothe plane containing the optical axis of the light radiated from thelight source 1 to get to the reflecting surface S2 and which is normalto the substrate 1.

[0164] In the present sixth embodiment, the optical axis of thetransmission light radiated by the light source so as to be reflected bythe reflecting surface S2 traverses a plane containing the optical axisof the light radiated from the light source 1 to get to the reflectingsurface S2 and which is normal to the substrate 1. Alternatively, theoptical axis of the transmission light radiated from the light source 1and which is reflected by the reflecting surface S2 may be inclinedrelative to the plane containing the optical axis of the light radiatedfrom the light source 1 to get to the reflecting surface S2 and which isnormal to the substrate 11. However, in this case, the reflectingsurface S2 needs to be inclined at the aforementioned angle of θ₂₃ tothe substrate 11 and also needs to be inclined relative to the planeperpendicular to the optical axis the light radiated from the lightsource 1 to get to the reflecting surface S2.

[0165] In the above-described sixth embodiment of the opticalcommunication apparatus 10G, in which the optical transmission medium 4can be arranged so that the optical axis of the reception light radiatedfrom the end face 4 a of the optical transmission medium 4 will beinclined relative to the plane containing the optical axis of the lightradiated from the light source 1 to get to the reflecting surface S2 andwhich is normal to the substrate 11, it is possible to raise the degreeof freedom in apparatus designing.

[0166] With the sixth embodiment of the optical communication apparatus10G, as with the first to sixth embodiments, it is possible to reducethe size and the production cost of the apparatus, while it is possibleto prevent the signal S/N ratio from being lowered.

[0167] Referring to FIGS. 17 and 18, a seventh embodiment of the presentinvention is explained. In the following description, parts orcomponents which are the same as those of the first embodiment aredepicted by the same reference symbols and are not explainedspecifically.

[0168]FIG. 17 is a diagrammatic view showing the schematics of anoptical communication apparatus 10E according to the seventh embodimentof the present invention.

[0169] In the above-described first embodiment, the reflecting surfaceS2 of the optical component 2 intersects the coupling surface S4 at anacute angle. In the present seventh embodiment of the opticalcommunication apparatus 10E, the region of the optical component 2 wherethe reflecting surface S2 intersects the coupling surface S4, that isthe at least a portion of the reflecting surface and the couplingsurface S4 close to the optical transmission medium 4, is provided witha cut-out surface S5. Meanwhile, FIG. 17 shows an example in which thecut-out surface S5 is provided in the optical component 2 in case therespective components of the optical communication apparatus 10E arearranged similarly to the arrangement of FIG. 1. However, the cut-outsurface S5 may similarly be provided on the optical component 2 of thethird embodiment shown in FIG. 8 or on the optical component 2 of thesixth embodiment shown in FIG. 14.

[0170] The optical communication apparatus 10E of the above-describedseventh embodiment is arranged in a casing 20, as shown in FIG. 18,showing a cross-section of the respective component parts of FIG. 17arranged in the casing 20.

[0171] In the above-described seventh embodiment of the opticalcommunication apparatus 10E, in which the cut-out surface S5 is providedat an area of intersection of the reflecting surface S2 of the opticalcomponent 2 and the coupling surface S4, it is possible to prevent thereception light radiated by the end face 4 a of the optical transmissionmedium 4 to proceed towards the photodetector 5 from being kicked by theoptical component 2, as well as to prevent the optical component 2 frombeing angled acutely. This gives a merit that the optical component 2can be improved in safety in operation to render the optical component 2more robust against destruction.

[0172] In the optical communication apparatus 10E of the seventhembodiment, as in the first to sixth embodiments, it becomes to reducethe cost and size of the apparatus as well as to prevent deteriorationof the S/N ratio.

[0173] Using FIGS. 19 and 20, an eighth embodiment of the presentinvention is explained. In the following description, parts orcomponents which are the same as those of the first embodiment aredepicted by the same reference symbols and are not explainedspecifically.

[0174]FIG. 19 shows a diagrammatic view showing the schematics of aneighth embodiment of the optical communication apparatus 10D. In theeighth embodiment of the optical communication apparatus 10D, shown inFIG. 9, a diffraction grating pattern is formed on the lens surface S1of the optical component 2.

[0175] In the present eighth embodiment, in which the diffractiongrating pattern is formed on the lens surface S1 of the opticalcomponent 2, the lens function ascribable to diffraction is added to thelens surface S1, with the result that the refraction power can beincreased, while the correction for aberration is facilitated.Meanwhile, the diffraction grating pattern such as used in the eighthembodiment may be provided on the lens surface S1 of the opticalcomponent 2 of each of the first to seventh embodiments.

[0176] The optical communication apparatus 10D of the above-describedeighth embodiment is arranged in a casing 20, as shown in FIG. 20,showing a cross-section of the respective component parts of FIG. 19arranged in the casing 20.

[0177] In the above-described eighth embodiment of the opticalcommunication apparatus 10D, in which the diffraction grating pattern isformed on the surface S1 of the optical component 2, the diffractivepower can be increased to reduce the size of the apparatus.

[0178] Also, in the present eight embodiment of the opticalcommunication apparatus 10D, as in the first to seventh embodiments, itis possible to reduce the size and the production cost of the apparatus,while it is possible to prevent the signal S/N ratio from being lowered.

[0179] Referring to FIGS. 21 and 22, a ninth embodiment of the presentinvention is explained. In the following description, parts orcomponents which are the same as those of the first embodiment aredepicted by the same reference symbols and are not explainedspecifically.

[0180]FIG. 21 is a diagrammatic view showing the schematics of anoptical communication apparatus 10H according to the ninth embodiment ofthe present invention. In the present ninth embodiment of the opticalcommunication apparatus 10H, shown in FIG. 21, the light convergingaction and the refractive action of changing the optical axis directionare afforded to the lens surface S1 of the optical component 2. That is,the lens surface S1 of the optical component 2 in the present ninthembodiment converges the light radiated from the light source 1 in thesimilar manner to the aforementioned respective embodiments, whilebending the optical axis of the light radiated from the light source 1so that the optical axis will be offset at an angle indicated by θ_(off)shown in FIG. 21. Also, in the present eighth embodiment, the angle θ₂₅which the optical axis after refraction by the lens surface S1 makeswith the reflective surface S2 will meet the aforementioned condition ofthe critical angle θc. Stated differently, in the present ninthembodiment, the angle θ25 which the optical axis after refraction by thelens surface S1 makes with the reflective surface S2 is designed to meetthe condition of the critical angle θc even though the optical axis ofthe light radiated from the light source 1 is bent so that the opticalaxis is offset an angle θ_(off) by the lens surface S1. In this case,the light radiated from the light source 1 to be incident on thereflecting surface S2 undergoes total reflection on the reflectionsurface S2. Moreover, in the eighth embodiment, the light reflected bythe reflecting surface S2 falls on the end face 4 a at substantially theright angle. The light reflected by the end face 4 a of the opticaltransmission medium 4 falls in this manner on the end face 4 a of theoptical transmission medium 4 at substantially the right angle, wherebylow dispersion is achieved.

[0181] On the other hand, in the ninth embodiment, the reception lightradiated from the end face 4 a of the optical transmission medium 4falls on the coupling surface S4 of the optical component 2 and on thereflecting surface S2 in this order. It is noted that the angle whichthe optical axis of the reception light radiated from the end face 4 aof the optical transmission medium 4 makes with the reflecting surfaceS2 is an angle θ26 not satisfying the aforementioned critical angle θc.In other words, in the present ninth embodiment, the reflecting surfaceS2 has a tilt satisfying the critical angle θc capable of reflecting thetransmission light incident via the lens surface S1 by total reflection,however, the tilt is such that the reception light radiated from the endface 4 a of the optical transmission medium 4 is transmitted since itfails to meet the condition of the critical angle θc. That is, thereception light transmitted through the reflection surface S2 isreceived by the photodetector 3 arranged on the optical axis of thereception light radiated from the end face 4 a of the opticaltransmission medium 4.

[0182] The above-described ninth embodiment of the optical communicationapparatus 10H is arranged in the casing 20, as shown in FIG. 22, showinga cross-section of the respective component parts of FIG. 21 arranged inthe casing 20.

[0183] In the present ninth embodiment of the optical communicationapparatus 10H, the transmission light falls on the end face 4 a of theoptical transmission medium 4 at substantially the right angle, wherebylow dispersion is achieved. Moreover, since the photodetector 3 can bearranged below the reflecting surface S2, the apparatus can be reducedin size.

[0184] Also, in the present ninth embodiment of the opticalcommunication apparatus 10H, as in the first to eighth embodiments, itis possible to reduce the size and the production cost of the apparatus,while it is possible to prevent the signal S/N ratio from being lowered.

[0185] Referring to FIGS. 21 and 22, a tenth embodiment of the presentinvention is explained. In the following description, parts orcomponents which are the same as those of the first embodiment aredepicted by the same reference symbols and are not explainedspecifically.

[0186]FIG. 23 is a diagrammatic view showing the schematics of anoptical communication apparatus 10I according to the tenth embodiment ofthe present invention. In the above-described ninth embodiment, thediffractive action of offsetting the optical axis of the light radiatedby the light source 1 is afforded to the lens surface S1 of the opticalcomponent 2. In the present tenth embodiment, the support base 12carrying the light source 1 is tilted to tilt the optical axis of thelight radiated from the light source 1 by an angle θ_(off) relative tothe substrate 11. By so doing, the lens surface S1 of the opticalcomponent 2 of the tenth embodiment having only the lens function as inthe aforementioned first embodiment can be used, whilst the angle θ₂₅which the optical axis of the outgoing light from the light source 1makes with the reflection surface S2 can be set to an angle satisfyingthe condition of the critical angle θc.

[0187] In the tenth embodiment, the reception light radiated from theend face 4 a of the optical transmission medium 4 falls on the couplingsurface S4 of the optical component 2 and on the reflecting surface S2in this order. At this time, the angle which the reception lightradiated from the end face 4 a of the optical transmission medium 4makes with the reflecting surface S2 is an angle θ₂₆ not satisfying thecondition of the critical angle θc. Thus, the reception light radiatedfrom the end face 4 a of the optical transmission medium 4 istransmitted through the reflecting surface S2 so as to be received bythe photodetector 3.

[0188] The above-described tenth embodiment of the optical communicationapparatus 101 is arranged in the casing 20, as shown in FIG. 24, showinga cross-section of the respective component parts of FIG. 23 arranged inthe casing 20.

[0189] In the present tenth embodiment of the optical communicationapparatus 10I, the transmission light falls on the end face 4 a of theoptical transmission medium 4 at substantially the right angle, wherebylow dispersion is achieved. Moreover, since the photodetector 3 can bearranged below the reflecting surface S2, the apparatus can be reducedin size.

[0190] Also, in the present tenth embodiment of the opticalcommunication apparatus 10I, as in the first to eighth embodiments, itis possible to reduce the size and the production cost of the apparatus,while it is possible to prevent the signal S/N ratio from being lowered.

[0191] A specified embodiment of the optical component 2 used in therespective first to tenth embodiments is hereinafter explained. In thefollowing description, parts or components which are the same as thoseof the first embodiment are depicted by the same reference symbols andare not explained specifically.

[0192]FIG. 25 shows a schematic perspective view showing the opticalcomponent 2A of the first specified embodiment used in any of the firstto tenth embodiments. In FIG. 25, the light source 1 is also shown.

[0193] On the lens surface S1 of the present first specified embodimentfacing the light source 1 is formed a lens portion S1 a responsible forthe lens function . The lens portion S1 a is formed only on the portionof the lens surface S1 illuminated by a light beam La of the lightsource radiated from the light source 1. The lens portion S1 a is shapedto conform to the far-field pattern of the light beam of the lightsource La and has different numerical aperture NA and differentfar-field patterns of the light beam of the light source La depending onthe far-field pattern of the light beam of the light source La. The lensportion S1 a converges the incident light beam by its lens function.

[0194]FIG. 26 shows the arraying state of the substrate 11, support base12, light source 1, optical component 2A, photodetector 3 and theoptical transmission medium 4 in case the optical component 2A of thefirst specified embodiment is applied to the aforementioned firstembodiment of the optical communication apparatus 10, whilst FIG. 27shows a perspective view of the optical communication apparatus havingrespective components shown in FIG. 26 arranged in the casing 20. In theembodiments of FIGS. 26 and 27, the transmission light radiated from thelight source 1 is reflected by the reflection surface S2 to fall on theend face 4 a of the optical transmission medium 4, as the transmissionlight is converged by the lens portion S1 a of the optical component 2A.FIGS. 26 and 27 show an embodiment in which the optical component 2A ofthe first specified embodiment is applied to the aforementioned firstembodiment, however, the optical component 2A may also be applied to thesecond to tenth embodiments.

[0195] In the optical communication apparatus having t the opticalcomponent 2A of the first specified embodiment, in which the lensportion S1 a shaped to conform to the far-field pattern of the lightbeam of the light source La is formed on the lens surface S1 of theoptical component 2A, the light beam of the light source La, issued fromthe light source 1, can be caused to fall wastelessly into the opticalcomponent 2A to fall on the end face 4 a of the optical transmissionmedium 4.

[0196]FIG. 28 shows a schematic perspective view of the opticalcomponent 2D of a second specified embodiment used in any of the firstto tenth embodiments. Meanwhile, FIG. 28 also shows a light source 1.

[0197] The optical component 2D of the present second embodiment isconstituted by a transparent member which is in the shape of a rodhaving its long axis extending along the direction of the optical axisof the light radiated from the light source 1, that is a transparentmember having a substantially circular cross-sectional shape when theoptical component 2D is cut in a plane perpendicular to the optical axisof the light radiated from the light source 1 to get to the reflectivesurface S2. This rod-like optical component 2D has its one end formed ase.g., a spherical lens surface S1 for producing the lens function, whilehaving the opposite end as the aforementioned reflecting surface S2having a pre-set angle for allowing for total reflection of the light.Since the optical component 2D of the present second specifiedembodiment is rod-shaped, the coupling surface S4, provided in theproceeding direction of the light reflected by the reflecting surfaceS2, is not planar but curved in profile.

[0198]FIG. 29 shows the arraying state of the substrate 11, support base12, light source 1, optical component 2D, photodetector 3 and theoptical transmission medium 4 in case the optical component 2A of thefirst specified embodiment is applied to the aforementioned firstembodiment of the optical communication apparatus 10, whilst FIG. 30shows a perspective view of the optical communication apparatus havingrespective components shown in FIG. 29 arranged in the casing 20. In theembodiments of FIGS. 29 and 30, the transmission light radiated from thelight source 1 is reflected by the reflection surface S2 to fall on theend face 4 a of the optical transmission medium 4, via coupling surfaceS4, as the transmission light is converged by the lens portion S1 a ofthe optical component 2A. FIGS. 29 and 30 show an embodiment in whichthe optical component 2D of the first specified embodiment is applied tothe aforementioned first embodiment, however, the optical component 2Amay also be applied to the second to tenth embodiments.

[0199] If the optical component 2D of the present second specifiedembodiment is used, the curved coupling surface S4 has the lensfunction, so that the transmission light radiated from the light source1, converged by the lens surface S1 and reflected by the reflectingsurface S2 is further converged by the coupling surface S4, as a resultof which it becomes possible to reduce the focal length from thecoupling surface S4 to the end face 4 a of the optical transmissionmedium 4. If, in the second and fourth embodiments, the opticalcomponent 2D and the photodetector 3 are arranged in the same area, withthe reception light radiated from the end face 4 a of the opticaltransmission medium 4 being made to fall on the optical component 2D viathe coupling surface S4, the reception light radiated from the incidenton the coupling surface S4 to fall on the end face 4 a of the opticaltransmission medium 4 is converged by the lens function furnished by thecurved surface of the coupling surface S4, as a result of which thedistance from the coupling surface S4 to the photodetector 3 can bereduced. Moreover, in the present embodiment, the reception light isincident on the photodetector 3, as the light is converged thereon,without being diffused, due to the lens function furnished by the curvedsurface of the coupling surface S4. Thus, the reception light can bemade to fall efficiently on the photodetector 3.

[0200]FIG. 31 shows a schematic perspective view of the opticalcomponent 2B of the third specified embodiment used in any of the firstto tenth embodiments. Meanwhile, FIG. 31 also shows the light source 1.

[0201] In the present third embodiment of the optical component 2B, thelens surface S1 facing the light source 1, has a columnar-shaped surfacehaving a curvature only in the x-direction, or a so-called cylindricalsurface. This columnar-shaped lens surface S1 operates for convergingonly the x-direction component of the incident light beam. Thus, in thepresent third specified embodiment of the optical component 2B, if thefar-field pattern of the light beam of the light source La iselliptically-shaped with the long axis being in the x-direction, thelight beam of the light source La is made to fall wastelessly on theoptical component 2B so as to be converged thereon.

[0202]FIG. 32 shows the arraying state of the substrate 11, support base12, light source 1, optical component 2B, photodetector 3 and theoptical transmission medium 4 in case the optical component 2B of thethird specified embodiment shown in FIG. 31 is applied to theaforementioned first embodiment of the optical communication apparatus10, whilst FIG. 33 shows a perspective view of the optical communicationapparatus having respective components of FIG. 32 arranged in the casing20. In the embodiments of FIGS. 32 and 33, the transmission lightradiated from the light source 1 is reflected by the reflection surfaceS2 to fall on the end face 4 a of the optical transmission medium 4, viacoupling surface S4, as the transmission light is converged by the lensportion S1 of the optical component 2B. FIGS. 32, 33 show an embodimentin which the optical component 2B of the third specified embodiment isapplied to the aforementioned first embodiment, however, the opticalcomponent 2B may also be applied to the second to tenth embodiments.

[0203] In the optical communication apparatus, employing the opticalcomponent 2B of the third specified embodiment, the lens surface S1 ofthe optical component 2B is formed as a columnar-shaped cylindricalsurface having the curvature only in the x-direction. Thus, as comparedto the above-described first specified embodiment of the opticalcomponent 2A, the optical axis adjustment tolerance in the y-directionof the optical component 2B is released to reduce the assembling cost.Also, in the optical communication apparatus employing the thirdspecified embodiment of the optical component 2B, in which the lenssurface S1 of the optical component 2B operates for converging only thex-components of the incident light beam, if the far-field pattern of thelight beam of the light source is elliptically-shaped with the long axislying in the x-direction, it becomes possible to cause the light beam ofthe light source La emitted by the light source 1 to be incident andconverged effectively and wastelessly in the optical component 2B.

[0204]FIG. 34 shows a schematic perspective view of the opticalcomponent 2C of the fourth specified embodiment used in any of the firstto tenth embodiments. Meanwhile, FIG. 34 also shows the light source 1.

[0205] In the foregoing explanation of the first to tenth embodiments,the optical component 2 is taken as an example, in which thecross-sectional shape of the lens surface portion S1 thereof obtained onslicing the optical component 2 in a plane perpendicular to thesubstrate 11 and containing the optical axis of light radiated from thelight source 1 to get to the reflecting surface S2 is curved andconvexed towards the light source 1, as shown in FIGS. 1, 2, 5 to 15 and17 to 20. It is however possible to use as the optical component used ineach of the first to tenth embodiments such an optical component 2C inwhich the cross-sectional shape of the lens surface portion S1 thereofobtained on slicing the optical component 2 in a plane perpendicular tothe substrate 11 and containing the optical axis of light radiated fromthe light source 1 to get to the reflecting surface S2 is linear, and inwhich the cross-sectional shape of the lens surface portion S1 thereofobtained on slicing the optical component 2 in a plane transverse to thesubstrate 11 and containing the optical axis of light radiated from thelight source 1 to get to the reflecting surface S2 is curved andconvexed towards the light source 1, as shown in FIG. 34.

[0206] Specifically, the present fourth embodiment of the opticalcomponent 2C has its lens surface S1 facing the light source 1 formed asa columnar-shaped surface having a curvature only in the y-direction inthe drawing, that is a so-called cylindrical surface. Thiscolumnar-shaped lens surface S1 operates for converging only they-direction component of the incident light beam. Thus, in the presentfourth specified embodiment of the optical component 2C, if thefar-field pattern of the light beam of the light source La, radiated bythe light source 1, is elliptically-shaped, with the long axis lyingalong the y-axis, the light beam of the light source La in particular isincident and converged wastelessly and efficiently in the opticalcomponent 2C.

[0207]FIG. 35 shows an arraying state of the substrate 11, support base12, light source 1, optical component 2C of the fourth specifiedembodiment shown in FIG. 34, photodetector 3 and the opticaltransmission medium 4 in case the optical component 2C is applied to theaforementioned first embodiment of the optical communication apparatus10, whilst FIG. 36 shows a perspective view of the optical communicationapparatus having respective components of FIG. 35 arranged in the casing20. In the embodiments of FIGS. 35 and 36, the transmission lightradiated from the light source 1 is reflected by the reflection surfaceS1, as only the y-direction component of the transmission light radiatedby the light source 1 is converged by the lens surface portion S1 whichis the cylindrical surface of the optical component 2C. FIGS. 35, 36show an embodiment in which the optical component 2C of the fourthspecified embodiment is applied to the aforementioned first embodiment,however, the optical component 2C may also be applied to the second totenth embodiments.

[0208] In the optical communication apparatus, employing the opticalcomponent 2C of the fourth specified embodiment, the lens surface S1 ofthe optical component 2C is formed as a columnar-shaped cylindricalsurface having the curvature only in the y-direction. Thus, as comparedto the above-described first specified embodiment of the opticalcomponent 2A, the optical axis adjustment tolerance in the x-directionof the optical component 2C is released to reduce the assembling cost.Also, in the optical communication apparatus employing the fourthspecified embodiment of the optical component 2C, in which the lenssurface S1 of the optical component 2C operates for converging only they-components of the incident light beam, if the far-field pattern of thelight beam of the light source La is elliptically-shaped with the longaxis lying in the x-direction, it becomes possible to cause the lightbeam of the light source La emitted by the light source 1 to be incidentand converged effectively and wastelessly in the optical component 2B.

[0209] The foregoing description is directed to the opticalcommunication apparatus of respective embodiments and optical componentsof the respective specified embodiments. However, the present inventionmay be optionally changed without being limited to the above-describedembodiments and specified embodiments. For example, in theabove-described embodiments and specified embodiments, the totalreflection of light is produced for reflecting the light on thereflecting surface S2 of the optical component 2 or the opticalcomponents 2A to 2D. However, the reflecting surface S2 may be processedwith mirror surface finishing to produce reflection to guide thetransmission light towards the optical transmission medium 4. Thepresent invention also is not limited to optical communication and maybe applied to a number of usages employing light transmission/reception.

[0210] Industrial Applicability

[0211] In the optical communication apparatus according to the presentinvention, in which the transmission light from a light source isconverged on a first surface of a sole optical component and reflectedtowards an optical transmission medium and in which the light incidenton the light reception element without falling on the second surface ofthe optical component is detected as the reception light, it is possibleto reduce the cost and size of the apparatus without lowering thetransmission/reception performance.

[0212] Also, in the optical apparatus of the present invention, thetransmission light from the light source is reflected by the totalreflection on the second surface of the optical component, so that, ascompared to the conventional apparatus employing e.g., a polarizationbeam splitter, it is unnecessary to form a high reflection multi-layerfilm or a polarization beam splitter film, whilst the film-forming costor the cost of bonding two prisms together to form a polarization beamsplitter can be dispensed with.

[0213] Moreover, with the optical apparatus of the present invention, inwhich the optical component is arranged above the light receivingelement, the apparatus can be further reduced in size.

[0214] With the optical apparatus of the present invention, in which thesecond surface of the optical component is inclined at an angle of 45°relative to the plane in which the optical component is arranged, theoptical component can be fabricated easily to enable further costreduction.

[0215] With the optical apparatus of the present invention, adiffractive pattern producing the light converging operation is formedon the first surface of the optical component, it becomes possible toincrease the refractive power further to enable further reduction insize of the apparatus. Moreover, since the aberration can be correctedeasily, it is possible to improve the S/N ratio.

[0216] With the optical apparatus of the present invention, the opticalcomponent is provided with a surface operating to prevent the componentfrom becoming acute in shape to prevent kicking of the reception lightto improve operational safety and to render the optical component lesssusceptible to destruction.

[0217] Also, with the optical apparatus of the present invention, thefirst surface of the optical component is shaped to conform to the lightspreading pattern of the light radiated from the light source, so thatthe light radiated from the light source is caused to be incident andconverged wastelessly and effectively in the optical component.

1. An optical apparatus comprising: a main body unit of an opticalapparatus; an optical transmission medium connector for connecting theoptical transmission medium to said main body unit of the opticalapparatus so that an end face of the optical transmission medium is at apre-set angle with respect to the main body unit of the opticalapparatus; a light emitting element fixed in said main body unit of theoptical apparatus and adapted for radiating the light; and a soleoptical element having a second surface facing said first surface and aconnecting surface interconnecting said first and second surfaces; saidsole optical element being fixed to said main body unit of the opticalapparatus; said first surface having the function of converging a lightbeam of light incident thereon from outside so that said light beam isfocussed at a position spaced a pre-set distance from said firstsurface; said light emitting element, optical component and the opticaltransmission medium connector being secured in said main body unit ofthe optical apparatus in a relative position such that light radiatedfrom the light emitting element is incident on said optical componentvia said first surface, the light incident on said first surfacetraverses the inside of said optical component, the light which hastraversed the inside of the optical component is reflected on saidsecond surface of the optical component towards the optical transmissionmedium connector, the light reflected on said second surface is radiatedfrom said coupling surface to outside the optical component, and thelight outgoing from said coupling surface is focussed on an end face ofsaid optical transmission medium.
 2. The optical apparatus according toclaim 1 further comprising: a light receiving element at a positionlying on the optical axis of the light radiated from the lighttransmission medium of said main body unit of the optical apparatus. 3.The optical apparatus according to claim 2 wherein said opticalcomponent is arranged offset from the optical axis of the light radiatedfrom said optical transmission medium.
 4. The optical apparatusaccording to claim 2 wherein said optical component is arranged on theoptical axis of the light radiated from said optical transmissionmedium, and wherein the light radiated from the optical transmissionmedium falls on said coupling surface in said optical component via saidcoupling surface to traverse the inside of the optical component to fallon the llight receiving element.
 5. The optical apparatus according toclaim 2 wherein said optical transmission medium connector connects saidoptical transmission medium at an angle with which the optical axis ofthe light radiated from the optical transmission medium is inclined withrespect to the optical axis direction of the light radiated from saidlight emitting element to get to said second surface.
 6. The opticalapparatus according to claim 2 wherein said optical transmission mediumconnector connects said optical transmission medium at an angle suchthat the optical axis of the light radiated from said opticaltransmission medium is included in a plane perpendicular to the opticalaxis direction of light radiated from the light emitting element to getto said second surface of said optical component.
 7. The opticalapparatus according to claim 5 wherein said light receiving element isarranged on the opposite side to the light emitting element with respectto said second surface of said optical component.
 8. The opticalapparatus according to claim 5 wherein said light receiving element isarranged on the side of the light emitting element with respect to saidsecond surface and wherein the light radiated from the opticaltransmission medium falls on the optical component via said couplingsurface to traverse the inside of the optical component to fall on thelight receiving element.
 9. The optical apparatus according to claim 1wherein said optical component has a diffractive pattern on said firstsurface.
 10. The optical apparatus according to claim 3 wherein saidoptical component further has a third surface which is provided at anarea between said second surface and said coupling surface which is atleast proximate to the optical transmission medium connector.
 11. Theoptical apparatus according to claim 1 wherein said first surface ofsaid optical component is such that the cross-section obtained onslicing the optical component in a plane passing through a first opticalaxis of light radiated from the light emitting element and getting tothe second surface and through a second optical axis of light radiatedfrom said optical transmission medium is convexed towards said lightemitting element.
 12. The optical apparatus according to claim 1 whereinsaid first surface of said optical component is such that thecross-section obtained on slicing the optical component in a first planeperpendicular to a second plane passing through a first optical axis oflight radiated from the light emitting element and getting to the secondsurface and through a second optical axis of light radiated from saidoptical transmission medium is convexed towards said light emittingelement, said first plane passing through said first optical axis. 13.The optical apparatus according to claim 1 wherein said opticalcomponent has a substantially circular cross-sectional shape which isobtained on slicing said optical component in a plane perpendicular toan optical axis of light radiated from said light emitting element andgetting to said second surface.
 14. The optical apparatus according toclaim 1 wherein said second surface exhibits total reflectioncharacteristics.